Ruddy Stucco Windows can be crafted in your Crafting Menu (opened by typing "Q" as the default key), after the according crafting-recipe has been unlocked by picking up/crafting Ruddy Stucco Walls for the first time (which in turn was unlocked by taking/crafting Stucco Walls). To craft 4 Ruddy Stucco Windows at once, you'll need (as of R26 in December 2015):